The conceptual framework for this protocol rests on the hypothesis that monoaminergic activity, as indexed by platelet monoamine oxidase (MAO), is a biological marker for vulnerability to alcoholism. Monoaminergic function may be determined by central or peripheral measurements of MAO, the enzyme that facilitates the conversion of monoamines (e.g., dopamine, norepinephrine, serotonin) to their metabolites. In children/adolescents, relationships betw. MAO activity levels and several risk factors for alcohol abuse have been found.